The S&P 500 lost about 57% from its 2007 peak to its 2009 low.
The S&P 500 reached a pre-crisis closing high of 1,565.15 on October 9, 2007. It later fell to 676.53 on March 9, 2009, a decline of roughly 56.8%, commonly rounded to 57%.
The collapse accompanied the global financial crisis, which began with problems in U.S. housing and mortgage lending. Losses on subprime mortgages spread through banks and structured financial products, while the failure or rescue of major financial institutions intensified investor fear.
The S&P 500 measures 500 large U.S. companies and is widely used as a broad benchmark for American equities. Its 2007–2009 decline was a bear market, not merely a single-day crash. The index eventually recovered, but the downturn remains one of the deepest in modern U.S. market history.